3D culture models of Alzheimer's disease: a road map to a "cure-in-a-dish"

Abstract

Alzheimer's disease (AD) transgenic mice have been used as a standard AD model for basic mechanistic studies and drug discovery. These mouse models showed symbolic AD pathologies including β-amyloid (Aβ) plaques, gliosis and memory deficits but failed to fully recapitulate AD pathogenic cascades including robust phospho tau (p-tau) accumulation, clear neurofibrillary tangles (NFTs) and neurodegeneration, solely driven by familial AD (FAD) mutation(s). Recent advances in human stem cell and three-dimensional (3D) culture technologies made it possible to generate novel 3D neural cell culture models that recapitulate AD pathologies including robust Aβ deposition and Aβ-driven NFT-like tau pathology. These new 3D human cell culture models of AD hold a promise for a novel platform that can be used for mechanism studies in human brain-like environment and high-throughput drug screening (HTS). In this review, we will summarize the current progress in recapitulating AD pathogenic cascades in human neural cell culture models using AD patient-derived induced pluripotent stem cells (iPSCs) or genetically modified human stem cell lines. We will also explain how new 3D culture technologies were applied to accelerate Aβ and p-tau pathologies in human neural cell cultures, as compared the standard two-dimensional (2D) culture conditions. Finally, we will discuss a potential impact of the human 3D human neural cell culture models on the AD drug-development process. These revolutionary 3D culture models of AD will contribute to accelerate the discovery of novel AD drugs.

Keywords: Alzheimer’s disease; Amyloid plaques; High-throughput drug screening; Induced-pluripotent stem cell; Neurofibrillary tangles; Three-dimensional culture.

Fig. 1

Recapitulation of Aβ and Tau pathology in a 3D human neural cell culture model of AD. Human neural progenitor cells (hNPCs) are virally transfected with APP and/or PSEN1 FAD mutations with either GFP or mCherry as a reporter for viral infection. These cells are enriched based on GFP and/or mCherry signals by FACS, and then differentiated in 3D Matrigel culture systems. Thin-layer (~100–300 μm) culture format is suited for immunostaining analyses and thick-layer (~4 mm) culture format is used for biochemical analyses. In 3D-differentiated hNPCs with FAD mutations, extracellular Aβ aggregates develop ~6 weeks of differentiation and robust increase in tauopathy is evident from ~10–14 weeks of differentiation

Fig. 2

Platform for AD drug screening in a 3D human neural cell culture model of AD. Typically, discovery of new AD drugs goes through three steps: Development and screening drugs in conventional 2D cell culture models of AD (Drug Discovery/Screening); followed by confirming the effects of drugs in AD transgenic mouse models (Preclinical Tests); and after their effects were confirmed both in cell culture and mouse models, drugs are further tested in humans (Clinical Trials). As compared to the conventional 2D cell cultures and animal models, 3D human cell culture models of AD can be more cost-effective and less time-consuming in developing novel AD drugs